The inability to cultivate Mycobacterium leprae in vitro has been a bottleneck in leprosy research, especially to obtain much needed information on therapy. The problem is further magnified by the increased occurance of dapsone resistant cases and their potential danger to the contacts. The mouse foot pad method currently being used is time consuming and expensive. All living material is intimately associated with, and dependent upon, adenosine triphosphate, ATP, and the ubiquity of this compound in living organisms renders it an excellent indicator of the presence or absence of life. ATP content quantitates the energy status of cells. Ultrasensitive bioluminescent quantification of ATP has made it possible to determine ATP from as few as one million host grown cells and thus, made feasible to interpret ATP data in terms of growth potential (ATP per viable cell) or functional biomass (ATP per aliquot) depending upon whether the organism is cultivable or non-cultivable. This biologic indicator of life is being widely used in medical technology, and also in cultivation studies on host-dependent microbes. It is proposed to adopt this methodology in order to obtain rapid information on the status of M. leprae form lepromatous patients under dapsone therapy. Advantage will also be taken of the fact that nine-banded armadillos (D. novemcinctus), when inoculated with leprosy bacilli, develop disseminated infection similar to lepromatous leprosy. Therefore, this animal will be used in the present study, as a model of human lepromatous leprosy, to evaluate applicability of ATP assay method is assessing the quality of M. leprae. This will enable to determine if armadillo can be used to study the effects of potential anti-leprosy drugs.